Thanks. I submitted the app to the Mac App Store and then after it had been accepted downloaded the App from the App Store directly. Once the App Store finished installing the app I found that now Quicklook started to work for my Custom File Types on the Mac that App Store installed the downloaded app onto. So it seems that in my situation XCode 16.3 installation during building and debug testing did not fully register the Custom File Types with the Finder.

Thanks Quinn. The IDELogRedirectionPolicy setting has fixed the NSLog problem. All working well now. Cheers.

This fixed it for me. Thanks.